Conventional digital display devices, such as liquid crystal display (LCD) monitors, receive analog signals from a video source (e.g., a personal computer) and convert the analog signals into a digital image. This conversion process involves various image processing steps including an analog to digital conversion. The analog-to-digital conversion is typically performed by an A/D converting device (e.g., an A/D converter). The A/D converter receives a system clock signal that controls the operation of the converter. Particularly, the pulses of the clock signal are used to sample the rising and/or falling edges of the analog input signal. The conversion process requires the sampling frequency and phase to be precisely synchronized with the analog video signals. Otherwise, the display image can be degraded overall, can include areas that are blurred, or can be misaligned to the display area of the display monitor. Over time, the analog input signal may vary with the phase of the clock signal due to environmental and other effects. As a result, the sampling may occur at improper intervals, thereby resulting in a blurry or noisy image.
Conventional display devices typically include a clock phase adjusting circuit, which detects the best clock phase at a given point in time, and outputs the best clock phase to the A/D converter, thereby correcting the displayed image. The clock phase adjusting circuit is typically activated by a user interface or control. The user interface or control may include a button or switch located in the housing of the display device. Alternatively, other manually-controlled user interfaces and input devices may be available. All of these prior systems suffer from drawbacks that are undesirable to users of the display devices.
For example, these prior art display devices require a user to monitor the displayed image for faults and operate the controls to perform the adjustment manually. This is inconvenient for the user. Furthermore, by the time the clock phase error becomes visibly apparent to a user, the clock is significantly out of phase, and the resulting clock phase correction will visibly and adversely affect the quality of the displayed image.
Therefore, it would be desirable to provide a system and method for adjusting the clock phase of a digital display which automatically adjusts clock phase in real-time and in a manner invisible to a user of the display.